Gas turbine engines, such as those used on jet aircraft, generally comprise an air intake port, a fan mounted on a hub near the air intake port and surrounded by a fan case, a low pressure compressor (LPC) section, an intermediate section aft of the LPC section, a high pressure compressor (HPC) section, a combustion chamber or combustor, high and low pressure turbines that provide rotational power to the compressor blades and fan respectively, and an exhaust outlet. The fan and LPC section may be operably connected to the low pressure turbine by an inner drive shaft which rotates about an engine center axis. A cone-like spinner may be mounted over the hub forward the fan blades to help guide air flow.
A series of platforms mounted to the hub between the fan blades define the inner radial boundary of the air flow path and help direct air flow to the LPC. Each platform may be secured to the hub by one or more pins. Since both the spinner and the platforms are attached to the hub, they rotate at the same RPM as the fan blades.
The platforms in some engines have a T-shaped axial cross-section. T-shaped platforms tend to rotate and twist for two reasons: First, the overall center of gravity (CG) of each T-shaped platform is off center with respect to the pin (the point of attachment of the platform to the hub). Second, the “local” CG, i.e., the center of gravity of an axial cross-section of the platform, varies in the axial direction, mainly due to the weight saving manner in which the platforms are made. The changes in overall and local CG can create high stresses and deflections at the leading edge of the platform.
For example, the trailing edge of the platform can twist in one direction and the leading edge can twist the other direction. Twisting of the platform can cause an undesirable change in the shape of the air flow path going into the LPC. Twisting of the platform also can cause air to flow underneath the platform, which can have aerodynamic, structural and heat transfer consequences. And with dense material platforms, due to tolerances, the CG can move around, making predicting the hot (operational) shape of the platform difficult. The present disclosure is directed at solving this problem.